Marine Diesel Engines - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 161

Contamination of the engine parts by sea water cooling must be prevented to
avoid dangerous corrosion. This technology is disappearing on ships and is being
more and more replaced by block cooling systems.
11.4 Operation Monitoring in Marine Diesel Engines
In current technology, cylinder pressure, exhaust gas temperature, concentration of
exhaust gas substances and several operation parameters of the main and the
auxiliary engines are monitored (see Table 11.5 ).
Modern main and auxiliary engines of a ship mean a highly complex, electroni-
cally monitored and regulated system. In the future, state-of-the-art technology for
pressure and temperature measurement can be completed with appropriate com-
bustion sensors to record the concentration of exhaust gas substances and discover
disturbances and deviations in engine, and exhaust gas after treatment system.
11.5 Development Tendencies
Although light weight materials are gaining importance in the construction of all
means of transportation, many different and non-replaceable conventional mate-
rials such as steel and aluminum are still used in the production of marine diesel
engines.
11.5.1 Conventional and New Materials
The development of engines with rising power increases the stresses on the valves.
The temperature of the inlet valves is 500-550C (932 - 1,022F) because of the
cooling effect of the fuel and air mixture. Outlet valves may reach operating
temperatures of about 850C (1,562F). For this task, Hardened Alloy Ferritic-
Pearlitic (AFP) such as martensitic-carbidic and austenitic-carbidic steels are being
developed with higher strength [ 33 ].
The advantages of aluminum cast products are its light weight and precise
tolerances. Aluminum alloys can be used for mechanical parts with small internal
diameters, e.g., for cylinder elements with small oil channels or for pistons with
small holes. The compressor wheels of the Exhaust Turbocharger (ETC.) can be
made also of aluminum alloys. Currently, cylinder heads are made of aluminum
and magnesium alloys instead of traditional gray cast iron. In the near future,
aluminum alloys will be used to strengthen crankcases [ 34 ].
Ceramics made of non-metallic, inorganic materials based on nitrides, carbides
and metal oxides are widely used for weight reduction, friction and wear of highly